1. Field of the Invention
This invention relates to a low recoil and low bore heat gun system. In particular, the low recoil gun system uses a delayed pressure release mechanism of the fired propellant charge. More particularly, the delayed pressure release of the exhaust gases causes a sonic rarefaction wave along the length of the barrel bore to arrive at the muzzle end of the gun barrel at a predetermined time, generally coincident with the fired projectile. The mechanism of the present invention allows a maximum amount of energy to be imparted into the fired projectile.
2. Brief Description of the Related Art
Recoil from a fired vehicle mounted gun system causes excessive motion of the vehicle, at times, creating the possibility of toppling the vehicle or causing extreme discomfort to the gun crew. As stated by Newton""s third law of motion, i.e., to every action there is always opposed an equal reaction, the momentum manifest within a gun system during the weapon launch is equal and opposite to sum of the momentum which is imparted to the projectile launched from the gun system, including the propellant gases that are subsequently ejected from the gun system. Minimizing the recoil increases the utilization of these gun systems.
Several methods are known to reduce the total forward momentum imparted during the launch of a projectile from a gun system. Momentum, as a vector quantity, does not dissipate as kinetic energy does, which is a scaler quantity. For a traditional gas gun, the launch momentum equals momentum imparted to the projectile, and the propellant gas that follows the projectile out of the muzzle. For a given projectile momentum, the total launch momentum may be reduced by redirecting the forward moving propellant gas to lower its forward speed, or reverse it.
Alternatively, some other inertia may be ejected out of the gun in the opposite direction from the projectile to achieve some degree of momentum cancellation.
All guns are subject to recoil, thus the problem has exited ever since the invention of the gun. The first known concept of a recoilless gun was sketched by Leonardo da Vinci (1452-1519) in which a gun fired two projectiles; one forward and one rearward, to balance the momentum. During World War I, Commander Cleland Davis, United States Navy, reduced the two projectile gun to practice. The Davis gun fired an ordinance projectile at the target, and a dummy projectile of Vaseline and lead dust, having an equal mass to the ordinance projectile, was fired in the opposite direction. The original Davis gun used a cannon that was open at both ends and loaded in the middle, and was apparently intended to target high altitude Zeppelins. Problems with the Davis gun include hazards to friendly forces from the rearward fired projectile and subsequent muzzle blast, added system weight from a second barrel and additional charge needed to obtain equal fire power of the projectile, and containing pressure in two directions. As such, the Davis gun has logistical burdens, munitions handling problems of heavy ammunition, a high system weight, and double length gun barrels that may limit mobility of a fighting vehicle.
Other developments in eliminating recoil from gun systems resulted in recoilless guns. Recoilless guns incorporated a nozzle in the breech to eject propellant gases out of the rear of the gun, permitting part of the propellant gas to flow backward and counter-balance the momentum of the fired projectile and any propellant that was propelled forward. A gun system that incorporated diversion of propellant gases through a nozzle located at the breech was developed by the Russians in 1936 using a design from a patent filed in 1917 by the Russian mathematician Riabouchinski. During World War II, United States Army Colonel Renxc3xa9 R. Studler, at the Research and Development Service of US Army Ordnance, developed a lightweight recoilless gun resulting in a shoulder fired weapon that could propel a three pound (1.36 Kg) explosive shell with a muzzle velocity of 1200 feet per second (366 m/s). The recoilless concept is used in the U.S. Army M40AD 106 -mm recoilless rifle that allows propellant gases to escape through a perforated chamber case between the projectile and breech, and the German LG 42 105 mm recoilless Howitzer that uses a bursting disk located at the breech to contain the propellant through ignition as opposed to a perforated chamber. Problems with recoilless rifles include poor ignition characteristics of propellant within the open chamber system, ejection of unburned propellant through the nozzle, erosion problems in large caliber direct-fire tank cannons from created pressures and temperatures (limiting recoilless guns to relatively low pressure applications), loss of substantial amounts of chemical energy from the propellant, added cost and weight from a perforated cartridge to contain the propellant while it burns, revealing back-blasts that also hazard firing crews, and limited nozzle design for recoilless rifles dictated by interior ballistic pressure.
Recoilless guns also have been developed using front orifices developed by the Frigidaire Division of the General Motors Corporation in collaboration with the Armour Research Foundation in the early 1950""s. The front orifices allow the ignition process to occur in a closed chamber, increasing efficiency. The gun initially behaves as a conventional weapon. However, shortly after the projectile begins to travel down the bore of the gun barrel, orifices integrated within the gun barrel that lead to a rearward facing contraction expansion nozzle are uncovered by the projectile obturator, allowing propellant gases to be vented from the gun and achieve forward thrust for recoil cancellation. Problems with a front orifice recoilless rifle include adequate ducting of escaping rearward muzzle gases at a substantial distance along the bore from the rear of the weapon, reduced pressure behind the launching projectile after the orifice is enabled and throughout the remaining duration of the ballistic cycle, limited chamber pressure, increased ammunition weight, and the initial imbalance in recoil loads requires a flexible, i.e., heavier and more complicated, mount to accommodate the initial rearward motion of the gun system prior to the uncovering of the orifices and their recoil mitigation effect. As such, recoilless and front orifice rifles present a logistical burden and munitions handling of heavy ammunition relative to that achievable with a traditional closed breach gun system, limited internal ballistic pressure, and an inability to operate in a closed-breech mode when firing low impulse rounds.
Muzzle brakes may be used to reduce firing impulses. French Colonel Chevalier Truielle de Beaulieu, in 1842, recorded the first known diversion of propellant gas using a crude muzzle brake to reduce the combined launch momentum. Muzzle brakes deflect the gases flowing out of the muzzle thus redirecting a substantial portion of the gas momentum. The efficiency of muzzle brakes generally ranges between 30 and 40 percent, with exceptional muzzle brakes achieving efficiencies as high as 70 percent. In this context, the muzzle brake efficiently is defined as the percentage reduction in the kinetic energy imparted to the recoiling gun system mass. During launch, the projectile is propelled by the high pressure propellant gases and when the rear of the projectile exits the main gun barrel it enters the muzzle brake. The muzzle brake allows the propellant gases to escape from behind the fired projectile. Through a combination of further gas expansion, and redirection of the gas flow, the net forward momentum of the propellant gases may be dramatically reduced, or even reversed by the muzzle brake. Problems with muzzle brakes include crew hazards from the excessive over-pressure of the blast, i.e., air disturbances or propellant gas moving at high velocity, loud noise and heat, creation of debris in the air obfuscating targets, added weight and cumbersome barrel redirection, limitations to end barrel use, and that high velocity gases remain to follow the projectile straight out of the muzzle brake unimpeded. As such, muzzle brakes present reduction of the recoil energy of a gun system by more than half, a health hazard, reduced vision in front of the gun, added weight to the end of the cannon and reduced projectile exit velocity (by reducing the pressure at the base of the projectile prior to exit from the gun system).
Heat imparted to the bore of a gun during firing may result in unacceptable temperature increase of the of the gun, and will accelerate the wear and erosion of the bore. The former consideration may limit the sustained rate of fire, while the latter may limit the life of the gun. The heat transfer to the gun is governed by complex partial differential relationships between the temperature, density, and velocity of the gas, and its interaction with the bore surface. The heat transfer coefficient as proportional to the velocity of the gases washing over the bore surface and the density of the gases. The net heat transfer integrates the rate of heat transfer over the duration of the exposure, therefore heat transfer also increases in kind with duration. Experimental evidence has shown substantial increase of bore erosion with bore temperature. In simple terms, the hotter the bore, the less resistant the material is to removal by wear and erosion. Current technology to reduce heat transfer to the bore surface during firing includes using cooler propellants and boundary layer cooling, both of which are not counter to the teaching of the present invention. Cooler propellants reduce heat transfer by reducing the temperature gradient between the propellant gas and bore surface, however, cooler propellants inherently have reduced impetus, i.e., energy. Boundary layer cooling includes ablative and smear cooling methods as outlined in A. J. Bracuti, xe2x80x9cWear-Reducing Additivesxe2x80x94Role of the Propellant,xe2x80x9d in Gun Propulsion Technology, Edited by Stiefel, AIAA Volume 109 Progress in Astronautics and Aeronautics, 1988, the disclosure of which is herein incorporated by reference. These techniques work by applying a fine coating to the bore surface during firing that is ablated away or by introducing favorable elements to the boundary layer near the wall to reduce convective heat transfer. Removal or sublimation of the ablative material is accelerated by the temperature of the propellant gases, and the velocity of the gas wash over the ablative material. It is well known from the Arrhenius equation and reaction kinetics that the rate of reaction increases exponentially with absolute temperature.
For large caliber armaments, heat transfer to the gun is resulting in the application of active cooling of the barrel, see for example, U.S. Pat. No. 5,837,921, to Christopher S. Rinaldi et al., entitled xe2x80x9cGun Barrel with Integral Midwall Coolingxe2x80x9d, as well as the development of specialized coatings to protect the bore from increased erosion.
Muzzle blast released after the projectile exits a gun appears to be a violent eruption of propellant gases. Muzzle blast generates flash, most predominantly secondary flash which occurs after hot propellant gases mix with ambient oxygen and re-combust. The column of hot gases following a round out of the gun result in shimmering that hampers the gunners ability to discern the damage inflicted upon the target. Dust raised by muzzle blast further complicates real time battle damage assessment. Blast deflectors have been applied to the muzzle end of guns to reduce these deleterious effects but are not totally effective.
Muzzle blast also unfavorably affects gun accuracy, such as yaw velocities being imparted to the projectile from transverse pressure gradients at shot exit and blast gases flowing forward over the fin surfaces after emergence from the muzzle (for fin stabilized projectiles) creating large destabilizing moment during a short time period.
In view of the foregoing, there is a need for improvements in minimizing the muzzle blast released after firing, the recoil of vehicle launched projectiles, and the heat transfer to the bore during firing. The present invention addresses these and other needs.
The present invention includes a low recoil low bore heat gun system comprising a barrel having a forward gun barrel section and a rear gun barrel section with the rear gun barrel section having a delayed pressure release mechanism for fired propellant charges.
The present invention also includes a projectile energy product created by the process comprising the steps of providing a low recoil and low bore heat gun system having a barrel with a forward gun barrel section and a rear gun barrel section, the rear gun barrel section having a delayed pressure release mechanism for a fired propellant charge and firing the projectile charge, wherein the exhaust gases from the fired projectile charge have a delayed release from the barrel.
The present invention further includes a method for imparting maximum energy to a fired projectile comprising the steps of providing a low recoil and low bore heat gun system having a barrel with a forward gun barrel section and a rear gun barrel section, the rear gun barrel section having a delayed pressure release mechanism for a fired propellant charge and firing the projectile charge, wherein the exhaust gases from the fired projectile charge have a delayed release from the barrel.